SCR Injector Deposit Detection via Pressure Drop Monitoring
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Solution Overview
Problem
The deposition of reductant compounds on the outlet nozzle of SCR injection systems due to low exhaust gas temperatures leads to reduced conversion efficiency and potential blockages, as the reductant can condense and form solid deposits, especially during low engine load conditions and low duty cycles.
Innovation Solution
Monitoring the SCR injection system by measuring pressure drop developments during purging operations and comparing subsequent pressure drop values to detect deposits at the nozzle outlet, allowing for the implementation of targeted deposit mitigation strategies such as increasing exhaust gas temperature or adjusting the dosing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the reductant injector operates at low exhaust gas temperatures, then the SCR system can function under low engine load conditions, but solid reductant deposits form on the outlet nozzle causing blockages and reduced conversion efficiency
Solution Approach 1:
The system performs preliminary heating of the outlet nozzle before reductant injection begins. By pre-heating the nozzle to a temperature above the dew point of the reductant, the system prevents condensation and subsequent deposit formation before the harmful effect can occur. This preliminary action eliminates the need for post-deposition cleaning while maintaining operational versatility.
Solution Approach 2:
The system applies preliminary anti-action by heating the outlet nozzle before reductant injection to prevent the harmful condensation effect. By maintaining the nozzle temperature above the dew point through pre-heating, the system counteracts the tendency of reductant to condense and form deposits, thereby preventing blockages before they can develop.
2Reliability
If the outlet nozzle is heated to prevent reductant deposits, then deposit formation is reduced, but additional energy consumption and system complexity increase
Solution Approach 1:
The outlet nozzle serves multiple functions: it is both the injection point for reductant and the heating element for preventing deposits. By integrating the heating function into the existing nozzle structure, the system avoids adding separate heating components, thereby reducing system complexity while maintaining reliable deposit prevention.
Solution Approach 2:
The system changes the temperature parameter of the outlet nozzle dynamically based on operational conditions. By adjusting the nozzle temperature according to the exhaust gas temperature and reductant injection rate, the system optimizes energy consumption while ensuring the temperature remains sufficient to prevent deposit formation under all operating conditions.
3Difficulty of detecting and measuring
If pressure monitoring is implemented to detect deposits, then deposit detection capability is improved, but system complexity and measurement precision requirements increase
Solution Approach 1:
The pressure sensor serves dual purposes: it monitors both the reductant supply pressure for normal injection control and detects deposit formation on the outlet nozzle. By utilizing the existing pressure sensing infrastructure for deposit detection, the system avoids adding dedicated detection equipment, thereby reducing complexity while improving deposit detection capability.
Solution Approach 2:
The pressure monitoring system performs multiple functions: it controls the reductant injection process and simultaneously detects deposit formation on the outlet nozzle. By making the pressure sensing system multi-functional, the system improves deposit detection capability without proportionally increasing system complexity, as the same hardware serves both control and diagnostic purposes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively detects and mitigates reductant deposits at the nozzle outlet, maintaining the efficiency of the SCR system by preventing blockages and ensuring continuous operation.
Implementation Method 1
monitoring pressure drop developments in the SCR injection system
Implementation Method 2
the redirected and leaked reductant may condense on it and the liquid components of the reductant may evaporate
Implementation Method 3
The high temperature of the exhaust gases may evaporate the liquid reductant
Data Source
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AI summary
A method for monitoring an SCR injection system (50) is disclosed. The method includes operating a pump (54), and measuring a first pressure drop value in the SCR injection system (50) during actuation of a reductant injector (32). A second pressure drop value in the SCR injection system (50) is measured during a further actuation of the reductant injector (32). It is determined to perform a deposit mitigation strategy based on the first pressure drop value and the second pressure drop value.